Shock-Tube and Modeling Study of Dimethyl Ether Pyrolysis and Oxidation

Pyrolysis and oxidation in fuel-rich and fuel-lean mixtures of dimethyl ether (DME) highly diluted with argon were studied behind reflected shock waves in the temperature range 950 - 1900 K at total pressures between 0.8 and 2.9 atm. The study was carried out using the following methods: l) time-resolved IR-laser absorption at 3.39 Jlm for DME decay and CH-compound formation rates, 2) time-resolved UV absorption at 216 nm for the CH3 radical formation rate, 3) time­ resolved UV absorption at 306.7 nm for the OH radical formation rate, 4) time-resolved IR emission at 4.24J1m for the C02 formation rate, and 5) a single-pulse technique for product yields. The pyrolysis and oxidation of DME, which were for very wide mixture compositions ranging from highly DME-rich to highly DME-lean, were modeled using a reaction mechanism with 178 reaction steps and 53 species including the most recent sub-mechanisms for formaldehyde, ketene, methane, acetylene, and ethylene oxidation. This and previously reported data were reproduced using this mechanism. The rate constant k5 = 4.5 x 10 14 exp (- 6.1 kcal/RT) cm 3 mor 1 s- 1 of reaction DME + OH -> CH30CH2 + H20 was evaluated.